1. Field of the Invention
The present invention relates to a drive apparatus for a vehicle including an engine output system that outputs power from an engine and a power transmission system that transmits the power from the engine output system to a driving wheel.
2. Description of the Related Art
Driving methods of a hybrid vehicle that uses an engine and an electrical motor as drive sources includes a series method and a parallel method. In the series method, the engines is driven as a drive source for generating electrical power, and the electrical motor is driven as a drive source for running the vehicle. In the parallel method, the engine is driven as main drive source for running the vehicle, and the electrical motor is driven as an auxiliary drive source for starting or accelerating the vehicle. In addition, a series-parallel method has been developed, in which the series and parallel methods are combined such that one or both of the engine and the electrical motor are driven in accordance with a driving state. In a hybrid vehicle that is driven using the series method or the series-parallel method, the engine can be stopped while the vehicle is running.
In a vehicle in which the engine thereof is stopped while the vehicle is running as described above, it is required to continue to supply hydraulic oil to an automatic transmission mounted in the vehicle. Thus, a drive source for an oil pump other than the engine is required. Accordingly, a drive apparatus for a vehicle has been developed, in which supply of hydraulic oil is continued even when the engine is stopped using an electrical oil pump that is driven by the electrical motor (for example, refer to Japanese Unexamined Patent Application Publication No. 2008-296907).
However, when an electrical oil pump is incorporated into a drive apparatus for a vehicle, a control system becomes complex and the size of a battery increases. This causes the size and the cost of the drive apparatus for a vehicle to increase.